DE69708290T2 - DRAIN VALVE - Google Patents

Description

The present invention relates to a drain valve and more particularly to a drain valve for use in an air brake system.

Effective operation of an air brake system requires the exclusion of moisture which may be drawn in by the (usually engine-driven) compressor or generated as a result of condensation.

Moisture can cause corrosion of components and otherwise interfere with proper operation. It is therefore common to provide an air dryer to ensure that air supplied to the system is of suitable quality. The air dryer usually comprises a replaceable canister of desiccant which is itself periodically regenerated by a volume of dry air. Such an arrangement is conventional.

It is desirable to maintain the air between the compressor and the air dryer under pressure when the compressor is not loaded; this arrangement ensures that oil is less likely to escape beyond the compressor piston rings under the influence of pressure in the engine crankcase and therefore contaminate the desiccant when the compressor is loaded.

A valve is provided between the compressor and the desiccant canister to keep the compressor outlet under pressure when the compressor is not under load. The valve is conventionally located in the body to which the canister is attached and is responsible for appropriate pressure control to open and close the connection between the compressor and the desiccant canister.

Typically, this valve is located below the desiccant canister and can collect excess moisture that drains down under gravity. If such moisture is not periodically removed, the valve can malfunction. The moisture is unable to escape to the atmosphere by simply venting, since the valve must remain pressure-tight to maintain the functionality of the air brake system. The present invention provides a means for removing such moisture.

According to the invention there is provided a vent valve comprising a housing defining a chamber, an air inlet and an air outlet opening into the chamber, an air passage defined in the chamber and providing fluid communication between the air inlet and the air outlet, and a closure member arranged to move in use in the housing between a first position in which the air passage is blocked and a second position in which the air passage is unblocked, the vent valve further comprising a signal port and movement of the closure member in use is effected by the presence or absence of a signal pressure at the signal port, and a collection container adapted to collect liquid in the vent valve, wherein the collection container comprises an ejection device adapted to eject liquid collected in the collection container to the outside of the valve, the ejection device being actuated in use by a predetermined change in pressure at the signal port.

The chamber may have a uniform cross-section. Accordingly, the closure member may comprise a piston which is slidably movable in a sealing manner within the housing. The air inlet and the air outlet may be arranged such that they open into the chamber at one end of the housing.

The air inlet and the air outlet may comprise concentric openings in one end of the housing; the closure member may define a sealing surface suitably arranged to seal over the openings.

The signal connection is preferably arranged in a side wall of the housing. The signal connection can be arranged in the side wall in such a way that it leads into the chamber on the opposite side of the piston from the air inlet and the air outlet.

Preferably, the side of the piston opposite the air inlet and the air outlet is serrated. A pressure surface may be provided adjacent the signal port and parallel to the side of the piston opposite the air inlet and the air outlet, the pressure surface being adapted to be pressed against the side of the piston in use. The pressure surface may be defined by the ejection device.

The toothing of the piston ensures that the signal connection is not blocked at the outermost piston position.

The ejection device may comprise a valve element mounted in the housing in an ejection passage in fluid communication between the collection container and the outside of the housing and an auxiliary collection container, the valve element being movable between a first blocking position in which the fluid communication between the collection container and the auxiliary collection container is blocked and the auxiliary collection container is in fluid communication with the outside of the housing and a second blocking position in which the collection container is in fluid communication with the auxiliary collection container and the fluid communication between the auxiliary collection container and the outside of the housing is blocked.

Preferably, the valve element is movable between the first and second blocking positions by means of a predetermined pressure difference between the signal port and the outside of the housing. The pressure at the signal port can be exerted on the valve element through the reservoir.

The valve element may be slidably movable in the housing. The valve element may be clamped and slidably movable between the first and second locking positions. The ejection device may further comprise resilient means for urging the valve element into the first locking position. The resilient means may comprise a coil spring. The ejection device may further be arranged such that a predetermined pressure difference between the signal port and the outside of the housing urges the valve element into the second locking position.

The ejection device may comprise a casing which is in sealing engagement with the housing. The The valve element can be clamped in the casing and can slide. The casing can comprise two sections between which the valve element is accommodated.

The signal connection may be suitable for receiving pressure signals from a control valve of the air brake system.

According to a second aspect of the invention, there is provided a drain valve comprising a valve element mounted in a housing, the housing defining a discharge inlet, a discharge outlet and an auxiliary reservoir, the valve element being movable between a first blocking position, in which the fluid communication between the discharge inlet and the auxiliary reservoir is blocked and the auxiliary reservoir is in fluid communication with the discharge outlet, and a second blocking position in which the discharge inlet is in fluid communication with the auxiliary reservoir and the fluid communication between the auxiliary reservoir and the discharge outlet is blocked.

The valve element may be movable by means of a predetermined pressure difference between the discharge inlet and the discharge outlet. Preferably, the valve element is urged into the first blocking position by means of an elastic element. The elastic element may comprise a coil spring.

A specific embodiment of a drain valve according to the invention, which realizes a drain valve according to the second aspect of the invention, is described below merely by way of example with reference to the drawing, wherein

Fig. 1 is a cross-sectional view of a drain valve according to the invention in a first operating mode in a vertical axial plane;

Fig. 2 is a cross-sectional view of the drain valve of Fig. 1, which is similar to Fig. 1, in a second mode of operation;

Fig. 3 is a cross-sectional view of the drain valve of Fig. 1, which is similar to Fig. 1, in a third mode of operation;

Fig. 4 is a cross-sectional view of the drain valve of Fig. 1, which is similar to Fig. 1, in a fourth mode of operation;

Fig. 5 is a cross-sectional view of a compressor for use in the invention in a vertical axial plane.

A drain valve 10 includes a substantially cylindrical housing 12. The housing 12 includes a first bore 14 extending axially from a lower end 20 through substantially half the length of the housing 12, and a second bore 16 having a smaller diameter than the first bore 14 and coaxial therewith, extending from the end of the first bore 14 to terminate proximally to the opposite upper end 22 of the housing, the side wall 13 having a shoulder 25 which is beveled at an angle of inclination to the axis of the housing 12.

An air inlet 24 and an air outlet 26 are provided at the upper end of the housing 12. The air inlet 24 has a circular bore and is coaxial with the bore 14, 16, and the air outlet 26 is concentric with the air inlet 24. The air inlet 24 and the air outlet 26 open into the bottom bore end face of the bore 14.

The drain valve 10 is arranged under a desiccant canister 70, of which only a portion is shown in Figs. 1 to 4 for clarity. The air outlet 26 is in fluid communication with the interior of the desiccant canister 70.

A signal connection 27 runs at the shoulder 25 in the radial direction through the side wall 13 to the bore 14, 16.

A cylindrical piston 28 is provided in the second bore 16. The piston 28 is arranged to slide axially in the second bore. The piston 28 includes an upper sealing surface 30 which can be pressed against the air inlet 24 and the air outlet 26, thus sealing them against fluid communication with each other. The piston 28 has two circumferential recesses 32 into which resilient fluid seals 33a, 33b are fitted to seal the piston with respect to the side wall 13, and a toothed lower surface 34 facing the lower end 20 of the housing 12. The upper seal 33a is an O-ring, the lower seal 33b is a lip seal.

A cylindrical casing 40 is provided in the first bore 14. The casing 40 is suitably arranged to fit sealingly into the first bore 14 and includes an upper surface 42 which is pressed against the beveled shoulder 25 of the housing 12.

The casing 40 is held pressed against the shoulder 25 by an annular spring 44 which is held in a recess at the lower end 20 of the housing 12.

Accordingly, when the piston 28 is moved downward in the housing, as shown in Figs. 2 and 3, it abuts the upper surface 42 of the casing 40. The recesses The toothed surface 34 therefore defines, with the upper surface 42, radially extending channels between the casing 40 and the piston 28, and these channels are in fluid communication with the signal port 27.

The shroud 40 includes a first axially extending circular ejection bore 46 extending downwardly from the top surface 42 for substantially two-thirds of the length of the shroud 40. A second axially extending circular ejection bore 48 of significantly smaller diameter extends from the base of the first ejection bore 46 to the base of the shroud 40, thereby defining an air passage 46, 48 through the shroud. A circumferential recess 50 is defined in the side wall of the first ejection bore 46, and the lower edge 52 of the recess 50 is beveled.

A cylindrical ejector piston 54 is enclosed in the first ejector bore 46 of the casing 40. The ejector piston 54 is enclosed in the bore 46 by a circumferential rib 56 of the upper end of the piston 54 which engages the recess 50. The rib 56 is substantially half the width of the recess 50 to allow constrained axial movement of the ejector piston 54 in the casing 40. The circumferential rib 56 is adapted to sealably engage the upper edge 53 of the recess 50 and an O-ring 58 is provided around the ejector piston 54 below and adjacent the rib 56 to alternately sealably engage the beveled lower edge 52 of the recess 50. There is a clearance between the peripheral wall of the rib 54 and the recess 50.

When the circumferential rib 56 is in tight engagement with the upper edge 53 of the recess 50, a main collecting container 59 is formed above the ejection piston 54 and within the first discharge bore 46. Alternatively, when the O-ring 58 is in sealing engagement with the lower edge 52, an auxiliary sump 61 is defined between the peripheral wall of the rib 54, the recess 50 and the O-ring 58.

Axial recesses 60 are provided in the peripheral surface of the ejector piston 54 to provide fluid communication between the recess 50 and the second ejector bore 48. A coil spring 62 is provided between the lower end of the ejector piston 54 and the lower end of the first ejector bore 46 to urge the ejector piston upwardly and into engagement with the upper edge of the recess 50. The coil spring 62 is disposed in a circular slot 64 in the lower end of the ejector piston 54.

It should be noted that for practical reasons, the shroud 40 is preferably made of two or more components, thereby enabling the shroud 40 to be arranged around the ejection piston 54 and thereby clamping the piston 54.

In the preferred embodiment, the bleed valve is used in an air brake system of a motor vehicle. The air inlet 24 receives air from a compressor, and the air outlet 26 discharges air to an air dryer containing a desiccant. A portion of a specific embodiment of a compressor for use in the invention is shown in Figure 5.

The compressor 100 includes a cylindrical housing 110 defining a cylinder 112 therein. At one end of the cylinder, a radially extending inlet 113 is in fluid communication with an annular suction chamber 114 and a radially extending outlet 115 is in fluid communication with with an annular discharge chamber. The suction and discharge chambers 114, 116 are coaxial with the cylinder 112.

The suction chamber 114 is in fluid communication with the cylinder 112 via an inlet valve 117. The cylinder 112 is in fluid communication with the discharge chamber 116 via an outlet valve 118. The valves 117, 118 are of the diaphragm type and are mounted such that flow is only possible through the valves 117, 118 from the suction chamber 114 to the cylinder 112 or from the cylinder 112 to the discharge chamber 116.

The cylinder 112 includes a reciprocating cylindrical piston 119. The piston is adapted to fit tightly within the cylinder and can slide therein. The piston includes the usual peripheral piston rings 120 to ensure that gases cannot escape beyond the piston 119. The piston 119 is connected via a connecting rod 121 to a drive of a vehicle engine (not shown) to provide reciprocating motion of the piston.

The first mode of operation of the drain valve 10, shown in Fig. 1, is when the piston 28 is in the lowest position in the housing so that the toothed surface 34 comes into contact with the top of the shroud 42 and the discharge piston 54 is urged by the spring 62 to its uppermost position. In that case, flow from the compressor 100 to the desiccant canister 70 via the inlet 24, the second bore 16 and the outlet 26 is not impeded. In the first mode of operation, any water that may enter the drain valve 10 is allowed to collect in the main sump 59.

Upon introduction of pressure into the valve via the signal port 27, forces exerted thereby urge the ejection piston 54 downward (Fig. 2) and into the second mode of operation. The O-ring 58 is in sealing engagement with the lower edge 52, thereby defining the auxiliary sump 61. Any water which has collected in the main sump 59 now flows through to the auxiliary sump 61 and collects therein.

When the pressure through the signal connection 27 increases, the piston 28 is pushed upwards and into its locking position (Fig. 3) and the third operating mode.

In the third mode of operation, the piston 28 seals the air inlet 24 and the air outlet 26, thereby unloading the compressor 100. The pressure in the cylinder 112 of the compressor 100 is high relative to the pressure in the crankcase, and therefore oil leakage from the crankcase that occurs around the piston is minimized. Therefore, oil cannot leak through to the desiccant and cause damage to it. Any water that does occur in the valve 10 will continue to collect in the auxiliary sump 61.

When the compressor 100 is to be loaded again, the pressure at the signal port 27 is reduced. First, the force exerted on the discharge piston 54 by the pressure at the signal port 27 drops below the force exerted by the spring 62. The discharge piston 54 moves upwards to the uppermost position with the peripheral rib 56 closely abutting the upper edge 53 of the recess 50. This is the fourth mode of operation. The main sump 59 is thus redefined and collects any water that may occur in the valve 10 and the Contents (if present) of the auxiliary collecting container 61 are discharged via the axial recesses 60 and the discharge outlet 48.

Upon further reduction of the pressure at the signal port 27, the piston 28 is released from sealing engagement with the air inlet 24 and the air outlet 26, and the piston 28 falls back to rest on the upper surface 42 of the shell 40. This returns the valve 10 to the first mode of operation.

By incorporating a drain valve as described in the preferred embodiment into a check valve, the check valve can be drained without a consequent loss of signal pressure.

Claims (10)

1. A drain valve (10) comprising a housing (12) defining a chamber, an air inlet (24) and an air outlet (26) opening into the chamber, an air channel defined in the chamber and providing fluid communication between the air inlet (24) and the air outlet (26), a closure member adapted to move in use in the housing (12) between a first position in which the air channel is blocked and a second position in which the air channel is unblocked, the drain valve (10) further comprising a signal port (27) and movement of the closure member in use is effected by the presence or absence of signal pressure at the signal port (27), and a collection container adapted to collect liquid in the drain valve, characterized in that the collection container is in fluid communication with the Signal port (27) and comprises an ejection device which is suitable for ejecting liquid collected in the collection container to the outside of the valve (10), the ejection device being actuated in use by a predetermined pressure change at the signal port (27). 2. Drain valve (10) according to claim 1, wherein the closure element comprises a piston (28) which is slidably movable in the housing (12) between the first and second positions. 3. A drain valve (10) according to claim 2, wherein the air inlet (24) and the air outlet (26) comprise concentric openings in one end of the housing (12), the closure element defining a sealing surface (3) which is suitable for effecting a seal over the openings. 4. Drain valve (10) according to any preceding claim, wherein the signal port (27) is arranged in a side wall of the housing (12). 5. A drain valve (10) according to any preceding claim, wherein the discharge means comprises a valve element mounted in the housing (12) in a discharge passage in fluid communication between the collection container and the outside of the housing (12) and an auxiliary collection container, the valve element being movable between a first blocking position in which the fluid communication between the collection container and the auxiliary collection container is blocked and the auxiliary collection container is in fluid communication with the outside of the housing (12), and a second blocking position in which the collection container is in fluid communication with the auxiliary collection container and the fluid communication of the auxiliary collection container and the outside of the housing (12) is blocked. 6. Drain valve (10) according to claim 5, wherein the valve element is movable between the first and a second blocking position by means of a predetermined pressure difference between the signal connection (27) and the outside of the housing (12). 7. Drain valve (10) according to claim 6, wherein the pressure at the signal port (27) is exerted by the collecting container on the valve element. 8. Drain valve (10) according to one of claims 5 to 7, wherein the valve element is slidably movable in the housing. 9. A drain valve (10) according to any one of claims 5 to 8, wherein the ejection means comprises resilient means (62) for urging the valve element into a first blocking position. 10. Drain valve (10) according to one of claims 5 to 9, wherein the ejection device comprises a casing (40) in tight engagement in the housing (12) which comprises two sections between which the valve element is received, and the valve element is slidably movable when clamped in the casing (40).